1. Field of the Invention
The present invention relates to semiconductor technologies, and more particularly to a method for correcting angle zero position in ion implantation equipment.
2. Description of the Related Art
Ion implantation is a viable replacement of thermal diffusion in diffusing or implanting atoms or molecules of selected dopants into a semiconductor wafer. During ion implantation, dopant atoms are accelerated by electrical energy and directed to the wafer.
The advantages of ion implantation process include accurate control of the amount of dopants, control of ion distributions, relatively decreased diffusion of dopant atoms in lateral directions than the thermal diffusion process, and uniform density of the implanted ions in the wafer. The ion implantation process is widely used for, e.g., controlling threshold voltage in metal oxide semiconductor (MOS) transistors, forming a well, isolation ion implantation, and forming a base region in bipolar transistors.
Equipment for the ion implantation typically includes a source module, an ion analyzer that extracts the produced ions by the source module, a beam gate for an ion path of the extracted ions, a target for directing the ions to the wafer surface, an end station module and auxiliary components.
Generally, the ion implantation equipment has an automatic angle control system for preventing an angle zero position from tilting. The angle control system monitors, by using five angle cups, ion beams traveling to the end station placed on the wafer, and corrects tilted angle and zero angle position. However, it is frequently observed that the zero angle is tilted even after it is corrected by the automatic angle control system. When the zero angle position is tilted, uniform ion implantation onto the wafer surface is not possible, thereby negatively affecting the electrical characteristics of semiconductor IC devices.